Magnetic penetration depth and flux-flow resistivity measurements on NaFe0.97Co0.03As single crystals

Okada, Tatsunori; Takahashi, Hideyuki; Imai, Yoshio; Kitagawa, Kentaro; Matsubayashi, Kazuyuki; Uwatoko, Yoshiya; Maeda, Akiko

doi:10.1016/j.physc.2013.04.074

Cited by 13 publications

(14 citation statements)

References 27 publications

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“…We note that the well-known positive slope in ρ ff (H) was observed in some iron-based superconductors like LiFeAs [21], NaFe 0.97 Co 0.03 As [22], BaFe 2 (As 0.55 P 0.45 ) 2 [23], and FeSe 0.4 Te 0.6 [24] using a microwave technique. Nevertheless, all these flux-flow studies are done at low temperatures, while our I-V measurements are limited to high temperatures, a few degrees below T c0 .…”

Section: (B)mentioning

confidence: 52%

Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe1−xCox)2As2

Huang¹,

Haney²,

Singh³

et al. 2017

Phys. Rev. B

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Measurements of the current-voltage characteristics (I-V ) were performed on Ba(Fe1−xCox)2As2 single crystals with doping level 0.044 ≤ x ≤ 0.1. An unconventional increase in the flux-flow resistivity ρ ff with decreasing magnetic field H was observed across this doping range. Such an abnormal field dependence of ρ ff is in contrast with the linear ρ ff (H) of conventional type-II superconductors, but similar to the behavior recently observed in the heavy-fermion superconductor CeCoIn5. A significantly enhanced ρ ff was found for the x = 0.06 single crystals, implying a strong single-particle energy dissipation around the vortex cores. At different temperatures and fields and for a given doping concentration, the normalized ρ ff scales with normalized field and temperature. The doping level dependence of these parameters strongly suggests that the abnormal upturn in ρ ff is likely related to the enhancement of spin fluctuations around the vortex cores of the samples with x ≈ 0.06.

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Section: (B)mentioning

confidence: 52%

Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe1−xCox)2As2

Huang¹,

Haney²,

Singh³

et al. 2017

Phys. Rev. B

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“…Based on the results described above, we have investigated the flux-flow resistivity of several Fe-SCs systematically in order to clarify how the novel features of Fe-SCs described above influence on ρ f (H). Here, we first summarize the obtained results for LiFe(As,P) [13,14], NaFe 0.97 Co 0.03 As (Co-Na111) [15], and SrFe 2 (As 0.7 P 0.3 ) 2 (P-Sr122) [16]. Each ρ f (H) of Fe-SCs increased almost linearly with H at low-H regions; ρ f /ρ n ≈ αH/H c2 .…”

Section: Introductionmentioning

confidence: 99%

“…Since a small amount of phosphorus substitution blurs the gap anisotropy, α of LiFeAs 0.97 P 0.03 (P-Li111) became slightly smaller than that of Li111; α P-Li111 ≈ 1.3 [14]. On the other hand, Co-Na111, which is considered to be a gapless SC with isotropic electronic structures, the gradient became almost unity; α Co-Na111 ≈ 1 [15]. In contrast to the nodeless Fe-SCs described above, P-Sr122 is considered to have a highly anisotropic gap structure composed by gaps with lines of nodes and deeply-warped nodeless gaps, and ρ f (H) increased rapidly at low-H; α P-Sr122 ≥ 2.5 [16].…”

Section: Introductionmentioning

confidence: 99%

“…The H-dependence of the flux-flow resistivity of P-Ba122 measured at T /T c ≈ 0.09 is shown in figure 3, where vertical and horizontal axes are normalized by the normalstate resistivity obtained by extrapolating ρ dc (T > T c ) to the low-T region and by the upper critical field, respectively. For comparison, the same plotsfor P-Sr122 (T /T c ≈ 0.08)[16], Li111 (T /T c ≈ 0.1)[13], and Co-Na111(T /T c ≈ 0.09)[15] are also shown. We already confirmed that the difference in the measurement temperature of T /T c ≈ 0.01 did not change their behaviors dramatically.…”

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confidence: 99%

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Penetration depth and flux-flow resistivity measurements of BaFe2(As0.55P0.45)2 single crystals

Okada

Imai

Takahashi

et al. 2014

Physica C: Superconductivity and its Applications

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We measured the surface impedance of BaFe 2 (As 0.55 P 0.45 ) 2 single crystals under finite magnetic fields by using a microwave technique. We found that the penetration depth increased as λ(T ) = λ(0) + A × T n with an exponent of n ≈ 1.7 in the temperature region of 0.1 < T /T c < 0.2. The observed fractional exponent can be understood by considering that this material has gaps with lines of nodes and nodeless gaps with large anisotropy. The fluxflow resistivity showed an almost H-linear dependence and a remarkably rapid enhancement in the low-H region; ρ f /ρ n ≈ αH/H c2 with a gradient of α > 2.5. Such a behavior is similar to that of SrFe 2 (As,P) 2 . By comparing these with results of 111-materials and SrFe 2 (As 0.7 P 0.3 ) 2 , it has been clarified that the gap anisotropy dominates the gradient α of iron-based materials.

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“…Critical current density (j c ) and flux-flow resistivity (ρ ff ) have each been widely studied both in conventional type-II superconductors [11][12][13] and in unconventional superconductors such as iron-pnictide systems [14][15][16][17][18][19][20]. Nevertheless, to our knowledge there has not been any study revealing and discussing the presence of a relationship between these physical quantities.…”

Section: Introductionmentioning

confidence: 99%

Relationship between critical current and flux-flow resistivity in the mixed state of Ba(Fe1−xCox)2As2

et al. 2017

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We studied the temperature and magnetic field dependence of vortex dissipation and critical current in the mixed-state of unconventional superconducting alloys Ba(Fe1−xCox)2As2 (0.044 ≤ x ≤ 0.100) through current-voltage measurements. Our results reveal that all the electric field E vs current density j curves in the Ohmic regime merge to one point (j0, E0) and that there is a simple relationship between the critical current density jc and flux-flow resistivity ρ ff : ρ ff /ρn = (1 − jc/j0) −1 , where ρn = E0/j0 is the normal-state resistivity just above the superconducting transition. In addition, E0 is positive for all five dopings, reflecting the abnormal behavior of the flux-flow resistivity ρ ff : it increases with decreasing magnetic field. In contrast, E0 is negative for the conventional superconductor Nb since, as expected, ρ ff decreases with decreasing magnetic field. Furthermore, in the under-doped and over-doped single crystals of Ba(Fe1−xCox)2As2, the parameter E0 remains temperature independent, while it decreases with increasing temperature for the single crystals around optimal doping (0.060 ≤ x ≤ 0.072). This result points to the co-existence of superconductivity with some other phase around optimal doping.

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Magnetic penetration depth and flux-flow resistivity measurements on NaFe0.97Co0.03As single crystals

Cited by 13 publications

References 27 publications

Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe1−xCox)2As2

Universality and unconventional enhancement of flux-flow resistivity in Ba(Fe1−xCox)2As2

Penetration depth and flux-flow resistivity measurements of BaFe2(As0.55P0.45)2 single crystals

Relationship between critical current and flux-flow resistivity in the mixed state of Ba(Fe1−xCox)2As2

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